Steel production
Due to the high demand for steel products from many industries, steel production is a constantly desired process of the metallurgical industry. Over the past 50 years, with the advancement of technology and the modernization of metallurgical processes, there has been a great deal of progress related to the reduction of harmful emissions associated with steel production and an increase in financial benefits.
Today, the process of making iron alloys in two stages involving smelting pig iron in a blast furnace or other process and steel in steelmaking processes is still in use.
Since the early 20th century, steel has been smelted in electric arc furnaces or in induction vacuum furnaces.
What is steel made of?
To make steel, it is necessary to obtain selected steel scrap from scrap yards, these are usually car bodies and other worn-out steel products.
The basic components of the feedstock are:
- steel scrap,
- fluxes or slag-forming materials, mainly lime,
- carburizers, e.g. coal, coke, anthracite,
- deoxidizers (aluminum, manganese, silicon),
- alloying additives,
- slag foaming agents.
The steelmaking process can be divided into three stages:
- Smelting
- Post-furnace processing
- Steel casting.
Steel smelting is carried out in an electric arc furnace, which provides lower energy intensity and plays an important role in steel waste recycling.
The furnace is loaded from the top with baskets, then the furnace vault is closed and electrodes are lowered to initiate the arc. The process of melting the charge is further assisted by supplying heat energy by means of oxy-fuel burners arranged in the furnace walls. In addition, the metal bath is blown with inert gas through nozzles embedded in the bottom of the furnace which accelerates the temperature equalization of the liquid metal and the course of chemical reactions. The liquid steel is then drained through a drain hole into a ladle, where another important process step takes place such as post-furnace treatment of the liquid steel.
Post-furnace treatment of liquid steel: this treatment yields steel with a low content of impurities such as sulfur, nitrogen, hydrogen, oxygen or phosphorus, and an appropriate chemical composition.
The final stage is the process of casting the steel.The steel can be cast into ingot moulds using the upward or siphon method, or it can be cast using the continuous casting of steel (COS) process, which significantly increases material yield and eliminates preliminary forming operations. In the COS process, liquid steel is poured into a water-cooled crystallizer; in addition, the stream is shielded by a protective tube to avoid contact with air. The outer surface of the ingot is subjected to water cooling, so that the partially cooled ingot can be picked up by drawing and straightening rollers. The finished ingots are subjected to cutting to a specified length, and in addition, after reheating in a continuous furnace, they can be rolled into a product with the desired final cross section.
For the production of alloy steels or metal alloys with special properties, induction furnaces are very often used. The feedstock is alloy steel scrap and pure components.
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